PERSISTENCE OF ARCHEAN LITHOSPHERE: CLUES FROM THE TRANS-HUDSON OROGEN IN CANADA

Although 2D geological maps suggest that a large proportion of the Paleoproterozoic-age Trans-Hudson orogen is comprised of juvenile crust, geophysical, geochronological, isotopic and structural data suggest that Archean-age crust dominates at depth. Furthermore, a large number of sutures and presumed sutures present within the orogen juxtapose Archean-age blocks with little intervening Paleoproterozoic-age material, suggesting that the latter was either subducted (recycled) or obducted and for the most part eventually removed by erosion. First-order (crustal-scale) structures such as faults and shear zones delimit a mosaic of Archean-age crustal blocks that may have formed isolated micro- or ribbon-continents prior to their accretion to larger continental masses (i.e., Superior, Rae and North Atlantic cratons). The above observations suggest that Archean continental crust appears to be far more resilient to recycling by tectonics than Proterozoic (and perhaps also younger) crust. Questions remain about the evolution of sub-continental mantle lithosphere (SCML), and whether it is also dominated by Archean-age mantle within Proterozoic mobile belts.